Distributed Lock Using Timestamps

Abstract

This chapter presents a distributed program that implements the distributed lock service in Chap. 11 over a fifo channel. It first solves a “distributed request scheduling” problem using Lamport’s timestamp mechanism, and then refines the solution to the distributed lock implementation. The request scheduling problem is as follows: potentially-conflicting requests arrive at different systems; they have to be served so that conflicting requests are not served simultaneously and every request is eventually served. Given a fifo channel connecting the systems, the timestamp mechanism provides a solution to this problem. The solution is easily refined to implement the distributed lock service, because the latter is a special case of the distributed request scheduling problem. The implementation is then further refined to use cyclic timestamps.